Liquid crystal polyesters, or those which exhibit optical anisotropy in the melt phase, are well known in the art. Numerous patents describe such polyesters and some are, for example, generally described in the article by W. J. Jackson, Jr. appearing in the British Polymer Journal December 1980 entitled, "Liquid Crystal Polymers IV Liquid Crystalline Aromatic Polyesters".
Some aromatic polyesters exhibit optical anisotropy in the molten state and can be melt spun into crystalline fibers which upon subsequent heat treatment further crystallize and substantially increase in tenacity. Such heat treated polyester fibers can be used for numerous purposes such as, for example, in tire cords and in other industrial and consumer products where high strength and low weight with its attendant economic and other advantages are desired. Specific applications for such type liquid crystal polyesters are as high strength reinforcements for numerous thermoplastic and thermosetting polymer materials.
In addition to their use in the form of fibers, such polyesters can also be formed by molding, for example, injection molding, into a wide variety of substrates which will have outstanding stiffness and toughness and strength.
In accordance with the present invention, an improved low cost, high performance thermotropic polyester, which is optically anisotropic in the melt, is manufactured and formed into fibers or molded into other useful articles using conventional thermoplastic polymer processing and forming technology.
The melt spinnable, liquid crystal polymers contemplated herein are of fiber forming molecular weight and exhibit optical anisotropy in the liquid phase and comprise recurring moieties. ##STR1## and, optionally, either or both of moieties III and/or IV wherein ##STR2## wherein R is an alkyl of 1-5 carbon atoms, e.g. methyl or tertiary butyl. Preferably the polymer consists essentially of moieties I, II and III and, most preferably, with the mole ratio of III to II being about 1.